Australia’s largest blackwood plantation!

I’m happy to be corrected on this claim. Forestry Tasmania established a very large blackwood plantation resource 20+ years ago, but I understand these have all since failed. So this ~25 hectare plantation in Robertson, NSW must now rate as the country’s largest planting.

But let’s go back to the beginning…

Blackwood is one of the most wide ranging tree species in Australia with a natural distribution from southern Tasmania, to the Atherton tableland in far north Queensland and across into South Australia. Heading up the east coast blackwood is increasingly confined to the cooler high altitude locations along the Great Dividing Range. But blackwood as a commercial species has been confined to Victoria and Tasmania.

So it came as a surprise when I was contacted earlier this year about a blackwood plantation on the southern Tablelands of NSW. The town of Robertson sits at an altitude of 750m on the eastern edge of the southern Tablelands with a mean annual rainfall of 1600mm and a climate not unlike parts of Tasmania, but with a summer rainfall bias. The district is renowned for its rich red basalt soils. The original native forest was more closely related to that found in the mountains of central Victoria 500 km to the south, with blackwood a common tree. Remnants of warm temperate rainforest known as the Yarrawa Brush occur in the district.

Photos of the plantation showed some challenges but also plenty of potential. Survival and growth seemed to be pretty good, but as is commonly the case, pruning had not been timely or maintained, and thinning was obviously needed. The owner had made a very significant investment and I was curious to find out more. I offered my help. Seven months later came the reply and last week I spent 2 days visiting Robertson.

Stunning!

My first experience with blackwood when I arrived, apart from seeing plenty of roadside and paddock trees driving into Robertson, was walking into the owners house and seeing an absolutely stunning timber floor. I didn’t recognise the timber so I took a guess and asked the owner if the floor was forest red gum.

“No!” He replied. “That’s local blackwood milled from the property”.

I was speechless!

Stunning “Robertson Red” blackwood floor.

This looked nothing like the blackwood floors I have previously seen. The uniform rich mahogany red-brown timber, with a distinctive grain, was unique to my experience. Part of the explanation for the uniform colour was that all the timber for this very large floor came from just 2 trees! But these two trees had identical timber colour. I have seen this mahogany red-brown colour in Tasmanian blackwood but it is not common, with Tasmanian blackwood mostly having a lighter golden-brown colour.

The next 24 hours showed me that this red-brown colour is the common colour of the local Robertson blackwood. I made sure that the owner understood how unique and precious this local feature was, which needs to be preserved and managed for the future. Research has shown that blackwood wood colour is strongly genetically controlled, so in my opinion this “Robertson Red” blackwood has commercial potential.

The owner and the property

The owner Andy Kennard has a passion for timber and growing trees which he inherited from his father, despite the family having no farming or forestry background. This property is the family’s third attempt at tree farming. He bought the property 18 years ago with the objective of growing quality timber and cattle. Most of the planting occurred around 10-13 years ago. To date the focus has been on a range of eucalypts and blackwood. The property also includes remnants of native eucalypt forest and warm temperate rainforest. The rainforest includes blackwood and other timber species such as northern sassafras and coachwood. The remnant native forest is now managed for conservation values with the occasional wind thrown tree milled for timber.

None of the people employed on the property have any forestry background or training so the tree-planting investment has been a big learning exercise. A point had been reached however where they didn’t know how to proceed or what to do next. And like many tree growers the thought of cutting down those precious trees was stalling any objective decision making. Beware the emotional attachment!

The Blackwood

The blackwood plantings are spread around the property in various paddocks on sites ranging from exposed ridge-top to sheltered lower slope and gully locations. The planting occurred between 2000 and 2003. All the plantings are on red basalt soils, with growth and performance varying widely even in the one paddock. A range of seedlots were used sourced from Tasmania, Victoria and NSW. No local Robertson blackwood seed was used. In a few areas eucalypt nurse crops were tried but these were a failure, due to the general poor growth of eucalypts on the property.

In the pure blackwood plantings initial stocking was 1100-1200 trees per hectare. In most locations survival was >95%. None of the blackwood paddocks have been fertilised under the current ownership. Early weed control is not known.

Early protection of the blackwood from domestic and wild animal browsers was a major issue. Standard farm fences proved sufficient to keep cattle out. But the wallaby, kangaroo and very active wombat populations have all been challenges requiring significant investment in fencing. Small amounts of ongoing deer damage is also apparent.

No thinning of the blackwood has yet occurred. Pruning has generally been OK but needed to be more timely and systematic. Most trees are pruned to at least 3 metres with pruning to six metres on the best sites. Given the lack of expertise and knowledge and the very large area to manage, the results have been very good. Cattle are grazed beneath the blackwood.

Results: poor to exceptional!

On the best sites blackwood growth and form is excellent, with 13 year old trees having diameters (dbh) ranging from 25-35 cm and heights of 12-16 metres. Some of the pruning on these trees has not been timely but nevertheless they are exceptional. At age 13 years these trees are half way to full commercial size!

Exceptional blackwood growth and form (30 cm dbh in 13 years).

In one paddock the trees have good uniform growth and form but a serious wattle grub attack followed by the inevitable cockatoo assault a few years ago has left at least 80% of the trees worthless. The owner now needs to assess what can be salvaged from this paddock. The cause of the wattle grub attack is unknown. Wattle grub is relatively rare in the other blackwood plantings. The trees look healthy and are growing well. Anecdotal evidence suggests that wattle grubs attack when trees are stressed or are getting old. So was it genetics or soils? Or was it just natural random chance?

On the ridge-top locations growth and form varies from ok to poor. Blackwoods hate growing in exposed windy positions where height and diameter growth and stem form become compromised. Robertson is on a high exposed plateau subject to strong winds. The property has some useful windbreaks but some of the high blackwood plantings are fully exposed the winds. Shelterbelts are needed to help improve the growth and form of these blackwood.

Despite the soils being derived from red basalt there are very obviously major soil issues for the blackwoods. This may be due to Ph, nutritional or soil structural issues or a combination of these. The owner is now organising soil testing across a range of sites both good and bad to see if the soil issues can be identified.

Records of the blackwood plantings are also in need to better management. Are the differences in blackwood performance due in part to genetics (seed source)?

Alternative Species

The owner has established a small arboretum where a range of local and other native tree species are being tested. Stand out performers for me were coachwood (Ceratopetalum apetalum), northern sassafras (Doryphora sassafras), silky oak (Grevillea robusta), red cedar (Toona ciliata), hoop (Araucaria cunninghamii) and Wollemi pines (Wollemia nobilis).

I’ve only ever seen coachwood and northern sassafras in native forest situations where they can be very impressive trees and certainly have a reputation for producing premium timber. So to see them planted in the open and growing very well was encouraging. These two species would be well worth considering on a small, specialised farm forestry basis. Silky oak, Red cedar and Hoop pine are more commonly seen in parks and gardens where their issues and potential are more commonly appreciated. Again at Robertson good growth can obviously be achieved given the right sites and treatment, when grown on a small scale.

10 year-old planted Coachwood. Not bad at all!

And finally Wollemi pine at 4 metres in 4 years shows that even this unique tree has potential for producing softwood of equivalent quality to Hoop pine, but with much easier pruning.

Wollemi Pine – 4 metres in 4 years!

With all of these species commercial rotations of 40-45 years might be possible if early performance is any indication, but with prices around $5,000+ per cubic metre for reasonable logs, these are still good investments.

And finally a word about eucalypts. For such a lush rich environment I saw very few outstanding eucalypts at Robertson. Amongst the species planted by the owner none seemed to be doing very well. I’m no eucalypt specialist but I can only put this down to soil problems.

Future

When these blackwoods were planted only New Zealand farmers and scientists were having any success growing commercial plantation blackwood. So for a novice enthusiast NSW landowner to plant 25 hectares was a brave venture. Despite this the results are certainly encouraging.

An action plan has now been drafted to get the blackwood management back on track. A thinning program has been sketched out, starting with the better performing stands. The scale of the thinning operation requires a mechanical approach, so research is needed to find an appropriate solution. Clearwood pruning will continue where it is still possible. Soil sampling and analysis will help identify what remediation is possible for some of the stands. Shelterbelts will be planted for the ridge top sites. An assessment of the wattle grub affected stand will determine what can be salvaged. Given that 82% of the trees need to be thinned anyway to get the stand down to 200 trees per hectare, there might still be something worth saving. Seed from the local Robertson blackwood will be collected for preservation and possible future planting. There was much discussion and a lot learnt by everyone involved including me.

So will Robertson NSW become a major centre for growing commercial blackwood?

No!

The land base is too small. Suitable areas are within about 5-10 km of the Illawarra escapement due to the terrain and steep rainfall gradient. But if enough landowners were interested there may be the potential for ~500 hectares of blackwood plantation. This could sustainably produce about 5000 cubic metres per year of premium blackwood sawlog. As a potential land use in this semi-rural landscape it is a relatively low-maintenance, high-value option. Close proximity to Sydney, and the Port of Newcastle and export markets, suggests that markets won’t be a problem.

There are still issues to be resolved including soil issues and determining the best genetics to plant, but hopefully growing Robertson blackwood should eventually be a profitable investment.

The visit to the Robertson blackwood plantation was definitely inspiring. Robertson clearly has blackwood growing potential. How the owner proceeds will determine whether that potential is realised and the challenges met. I’m looking forward to assisting and following progress here over the coming years.

22 responses to “Australia’s largest blackwood plantation!”

Cracker of a post! Love to see farm foresters having a go at less common species. We’re planting allocasuarinas, banksias, callistemons, some less common acacias and some exotics as well as blackwood, silver wattle, bluegum, spotted gum, coastal mahogany, yellow stringybark, pinus radiata and so on. I measured some ~23 year old Toona ciliata on a private property in the Yarra Valley at 60cm DBH a few months ago. And no tip moth! We have about 50 seedlings from this source we will plant next autumn.

The wattle grub at Robertson is a bit concerning. I saw some otherwise healthy looking 4-5 year old regen silver wattle on a property near Dollar in the Strezleckis a few months ago. Cockies had ripped into a few to get grubs.

The blackwood growth rates at Robertson don’t surprise me. I suspect sites in warmer climes than Tasmania with good soil and rainfall may show a bit faster growth rates.

Best of luck to the Robertson folks and I look forwards to reading about their progress.

Thanks for the positive feedback David. As I said the trip to Robertson was inspiring. It would make an ideal location for a field day if it wasn’t so far away. So much to learn, so much achieved and much to still achieve in the future.

David,
A note re. alternative species.
It’s certainly good to try alternative species. There is still plenty to be learnt, and certainly plenty of commercial potential still to be discovered.
But don’t get carried away!
Too many species, too much complexity/diversity and you will quickly become lost and overwhelmed. You will lose focus.
I would recommend no more than 6 alternative species at most. Select them with care and think seriously about what you are trying to discover/achieve. If they aren’t performing as expected after 4-5 years, then get rid of them and try something else.
Spread your efforts too thinly and you will lose focus.
I like Andy’s idea of a simple arboretum with ~15 different species and about 4-6 trees per species, just to get a basic idea of how each species grows.

I give credit to the landowner for having a go. However, several lessons can be learnt. Firstly, get some serious advice before starting. 25ha is a lot of blackwood, a significant investment and if not done properly a large financial loss is likely. From the photos it appears as though every tree has been pruned to 3m. With a stocking of 1000+ sph, it’s way too many! Pruning to 3m should only have been undertaken on the best 400 sph at most, with pruning beyond 3m concentrated on the best 200 sph. I don’t want to sound negative but it’s important to understand the economic impact of pruning. Consider 2 stands of pruned blackwood, one at 200 sph and another at 300 sph, all pruned to 6m. At the end of a 35 year rotation the clearwood volume will be very similar, yet considerably less money has been spent on pruning only 200 sph. The return on pruning investment is far greater at the lower stocking. I’ve made errors with trees and learnt from my lessons. If we recognize and share our mistakes as well as positives, all growers will benefit.

Hi Gordon, at your request I will make some comments from across the ditch. Your photos show some impressive trees, and the growth rates are about what we would expect on a decent blackwood site in New Zealand. A provisional growth model from Scion based on several plantations has a mean DBH of about 32 cm at age 13, which is what you have. At 200 sph that would deliver a mean DBH of a bit under 60 cm at age 35. This is of course conditional on thinning, and I note that you are planning to start a thinning program. Delaying thinning is one of the worst mistakes we make, and that forces the live crown to retreat, and condemns the trees to slow diameter growth. I’m sure there must be many sites in Tasmania and the mainland that could deliver a similar growth rate.
On the question of varying performance, that is common when blackwoods are planted across a large area of mixed topography. Although blackwoods can survive across a range of sites, their performance is strongly influenced by site conditions, and I think they should be regarded as highly site-selective. Back in 1979 Ian Nicholas from Forest Research spent a year looking at blackwood responses to site conditions, and found that shelter from prevailing wind is the most critical factor. That might explain some of the variation at Roberton. Over here, sheltered gullies and lower valley slopes produce the best results, and exposed ridges should be avoided.
I will be interested to hear the outcome of the soil analysis. A number of studies have been carried out in NZ on soils in blackwood plantations, including foliar analyses, responses to fertilisers, etc. The one that seems to matter is P, which tends to get locked up in clay soils, and the recommendation is to use 150 gm per tree soon after planting.
Another possible explanation for varied performance is provenanve. I note that provenances from Tasmania, Victoria, and NSW have been used. I have a provenance trial on my property at Pirongia, near Hamilton, established with Ian Nicholas, and comprising over 60 provenances from sites in Australia extending from southern Tasmania to Queensland.
There are prominent differences between them. When measured for growth rate and form, the Northern Tasmanian trees performed best, and the worst are from NSW and Queensland. Of course that might not apply to blackwoods planted in NSW, where there is a different climate pattern. The Chinese have carried out extensive provenance studies on blackwood (it is worth noting that they have identified blackwood timber as closely matching their most desirable furniture timbers). They found that Queensland provenances performed best in the SouthEast. The climate there, like Queensland has predominately summer rainfall. So I guess if you are planning further planting in NSW it might be worth trialling a few different sources before getting too involved.
That should certainly include locally sourced material. The colour in your photo is quite unusual and very interesting, and if you can replicate that you might have a niche market.
I assume Stu is Stu Swanson. Good to hear from you Stu.
Ian Brown

I have a block in Gippsland (Strzeleckis) with some mature blackwoods (which seem to fall over once they get to a certain age), some planted in the last ten years and we plant to plant some more. I would be grateful if you could perhaps comment on a couple of items.

At 32cm DBH at 13 years that’s an average DBH/annum of 2.5cm in the first 13 years. And to get to 60cm at 35 years would be a bit over 1cm DBH/annum in the next 22 years. Do all well-managed plots on good sites show this slowdown? If the 2.5cm/annum could be maintained that would be a much faster rotation to 60cm.

Did you get your provenances from the ATSC? I can collect seed from our property, other local trees and the revegetation nurseries generally have blackwoods but I would like to use a provenance proven to have good growth and form in a managed plantation in local conditions. I haven’t had much success in this regard for our area.

How have you found best to apply the phosphorus? We have mainly clay soils. I haven’t done any soil nutrient analysis as we have good pasture growth, large existing mature trees and recently planted trees on the block are growing well but I could trial some plots with and without an application of fertiliser.

Hi David,
Growth
The growth model shown in Nicholas & Brown (Blackwood Handbook) (p. 68) does show diameter growth slowing with age. But the model shown is only for one site.
In
Berrill, J-P.; Nicholas, I.D.; Gifford, H.H. 2007. A preliminary growth model for New Zealand grown Acacia melanoxylon. New Zealand Journal of Forestry Science 37(1): 37-56.http://www.scionresearch.com/__data/assets/pdf_file/0019/5554/03BERRILL37137-562007.pdf
they show declining diameter growth with age even on very good sites (p. 52). So the current annual increment (CAI) at any one time is often different to the mean annual increment (MAI) over the life of the tree. It’s the MAI that is important.

One of my objectives with the coop is that farmers who have native blackwood on their property will collect seed and we can start up a coop seed bank. Similarly with clones. If we find a good colour (eg. Robertson Red) or better yet some fiddleback then the coop is the natural place to help develop this. But all that is in the future.

Soil
I think any landowner should do soil testing and start to understand the nature and diversity of soils they are managing. Just good business really.

Your question regarding slowing diameter growth with age is due to competition and effective biological limits. Just as a given area can only grow so much grass and support so many stock, so it is with trees. As competition between trees increases, diameter growth slows and self-thinning eventually sets in.

The easiest way to measure competition is Basal Area. BA can be measured as the average cross sectional area of stems at 1.3m, multiplied by the stocking / ha. At a stocking of 200 sph, BA increases with average tree diameter as follows.

The increase in BA with diameter isn’t a straight line but an exponential curve. Below a BA of ~15 there isn’t a great deal of competition between trees. Between 15 and 25 the competition is setting in. 25-35 and the competition is high. 35-45 and tree-tree competition starts to become severe. A BA of 45 is the typical limit for native forest blackwood. It can go above this but only on very high quality sites, the highest BA measured in native forest in Tasmania is 60. Plantations can exceed this, with a BA of 75 measured in a 96 year old stand of pure blackwood in NZ.

As far as seed goes for further planting, I would recommend you collect seed from your local area plus some low elevation NW Tasmania seed, plant both and see how they compare. I’m involved with the harvest of blackwood in NW Tas and will be collecting some seed from an exceptional stand in the new year. This stand has excellent form (keeping in mind form is influenced by environment more than genetics), a height of ~35m and diameters up to 1m. It is growing on a slightly raised, well drained clay loam immediately adjacent to high quality blackwood swamp forest. This area was partially harvested last year and the timber quality / colour from these trees is excellent. If you wish to get hold of some of this seed let me know.

Fertilising – apply 150g of super around seedlings at planting (~0.5m from the seedlings, not right at the base), but only in conjunction with good weed control.

To clarify Ian Browns comments, after I posted this story Ian and I had an exchange of emails which I thought provided a useful New Zealand perspective on the story. So I asked Ian if he would post a comment on the website. Lots of useful insights and suggestions. Thanks Ian.

Thanks for the comments, Stu. So it should be possible to manage stand BA to maintain increment in DBH/annum to some degree by continually thinning to a smaller number of trees to maintain the BA within lower levels. Whether or not this would be profitable would depend on the eventual harvest volume of a smaller number of big diameter trees and the price/m3 this volume of timber would attract vs the price/m3 from a larger volume of smaller logs. And the extra thinning costs offset by commercial returns from later thinnings.

I guess one question is whether any blackwood plantation growers (perhaps in NZ) have managed their plots with the intention of producing some large diameter logs and how did they go. We have what appears to be a very good site for growing blackwood and the space to do some trials so I could dedicate some area to some experiments along these lines.

I would like to get some of the NW Tasmania blackwood seed you mention. And we will collect some local blackwood seed from our place and other sources once it’s ripe. There’s a roadside tree with an enormous diameter not far from us.

On a related note, I measured a paddock silver wattle on our block at 72cm DBH the other day. A good size for this species in Vic. We collected a load of seed from the larger dealbata’s we’ve identified with some also from younger trees with good form. We’ll do some direct seeding as an experiment.

Hi David
Thinning to lower the BA / competition will enable increased diameter increment on retained trees. As you suggest, what are the economic impacts? Modelling can be done to give indications and trials will give long term answers. However, don’t get too hung up on it at this stage. Get the trees in the ground with adequate numbers and spacing, get the pruning and thinning done on time and produce a stand of well-formed blackwood pruned to 5-6m at a final stocking of 150-200 sph by age 10. When they are 45-50cm (age 25-30) it may be time to consider clearfell vs thinning options. I’m sure most growers in NZ are looking at clearfelling once 50-60cm diam trees are attained.

Fully agree with Stu. We still have a lot to learn and much confidence to build. Keep it simple and focus on doing the best job you can. Get the trees planted and growing as quickly as possible. Good weed control is absolutely essential. For the foreseeable future lets follow the New Zealand model.

The increase in BA with diameter isn’t a straight line but an exponential curve. Below a BA of ~15 there isn’t a great deal of competition between trees. Between 15 and 25 the competition is setting in. 25-35 and the competition is high. 35-45 and tree-tree competition starts to become severe.
”

at 50cm DBH they are well into what Stu described as severe competition. So depending on the price/m3 for large diameter logs – which on the data from IST Gordon has been reporting is non-linear with diameter – keeping the BA down may help to grow larger logs quicker and get a better return.

Some of the graphs mentioned appear to show a marked slowdown in DBH before the severe competition phase. So it’s possible that there’s an inherent restriction affecting DBH/annum of some other nature that the trees experience.

And I think its possible that while a one-size-fits-all blackwood silvicultural model is a good start, if a grower has a site that is very well suited to growing blackwoods then its worth exploring options that may improve the result by making use of the site characteristics to optimise yield. Particularly if the grower has the time and expertise to more closely manage the plot.

It would be very interesting to see results from any NZ growers who have managed a high quality blackwood plot for optimised log size.

David,
As Ian Nicholas says in the NZ video, it’s not just about managing for BA/diameter growth, but also about managing for good crown structure. In the video Ian drives home the message that early thinning and a generous spacing for most of the rotation is needed to allow blackwood to develop a broad flat stable crown structure. Too much competition results in blackwood developing a narrow vase-shaped crown with acute branch angles that are very prone to wind damage. Only on very sheltered sites would I advocate multiple thinnings and a more complex management approach.
In most cases we don’t really know what the “site characteristics” are until we get to the second rotation, and with climate change the second rotation will be different to the first anyway. Keep it simple!
Cheers,
Gordon.

Recoverable clearwood obviously involves pruning. Pruning is an investment that needs to generate a return. No point in harvesting a pruned tree if the recoverable clearwood is insufficient. A minimum small end diameter of ~40cm is required to generate sufficient recovery, hence a minimum dbh of ~50cm is required at harvest (assuming pruning to 5-6m).

Economics – silvicultural input has to be minimised whilst still generating a stand of well-formed trees. $ invested and time is the economic cost. Returns are based on recoverable clearwood and wood quality (i.e. what will someone pay for the timber) compounded back over time to when the original $ were invested.

Site characteristics can be determined even before planting the first rotation: soil, rainfall, aspect, shelter, existing native vegetation all provide a guide as to how well the trees will grow. Crown structure can be significantly influenced by silviculture, in addition to genetics and site. No need to wait till the second rotation to work it out.

They were on the block of a guy who used to grow and supply tree species from northern NSW. He’d planted a few toonas on his block that have done well. The toonas I have from him had sprouted in his gutter! He hasn’t had any seeds or seedlings this year.

You can get toona ciliata seed from a number of seed suppliers. You could get a nursery to custom grow these for you in Hiko cells or forestry tubestock. Or have a go yourself. I’ve seen T. ciliata doing well in gullies in the Otways. And the trees in the Valley were doing very well. They were in a shaded gully with other planted trees which probably helped.

It might also be worth trying Toona sinensis or Chinese cedar. This is a related species. Seeds are also available from suppliers.

Good luck and let us know how you go

David

This is a site about blackwoods. I grew up in the Dandenongs and have spent a lot of time in the Valley over the years and now I think of it I don’t remember ever seeing a really big blackwood there. Or a big silver wattle for that matter. Not like what you get in the Strzeleckis or Tasmania. Not to say that you couldn’t grow a big acacia in the Valley with appropriate silviculture.